Compositions for protection of metals against corrosion



Patented June 23, 1953 COMPOSITIONS FOR PROTECTION OF METALS AGAINSTCORROSION Aaron Wachter and Nathan Stillman, Berkeley,

Calif., assignors to Shell Development Company, San Francisco, Calif., acorporation of Delaware 1 No Drawing.

Claims.

The present invention relates to novel compositions comprising asubstantially solid material which contains, or is impregnated or coatedwith a vapor phase inhibitor which inhibits the corrosion of metals.More particularly stated, the present invention is concerned withvarious absorbent materials, e. g., cellulosic substances and theirderivatives (modified paperacard-board, fibreboard, wood, cotton, clothand the like) which are coated, impregnated, or otherwise contain one ormore of the vapor phase inhibitors described below. I

Our copending applications Serial No. 663,608, filed April 1, 1946,Serial No. 668,015, filed May 7, 1946, and SerialNo. 675,886, filed June1, 1946, disclose and claim variou methods of inhibiting corrosion bythe introduction of certain types of vapor phase inhibitors; the presentinvention covers various substantially solid materials containing thesevapor phase inhibitors, said materials being suitable for packaging orenclosing metals. 7

During storage, handling, transportation, etc. of objects having metalor metal-containing surfaces, especially those of various steels,aluminum, etc, it is often necessary to prevent the corrosion of thesemetals. Heretofore, the various methods used for this purpose have beenunsatisfactory because of inadequate prevention of corrosion,ClliIlbElSOlIiGllBSS, and/or the necessity of using an excessive amountof labor and expenditure of time. v

Partially or completely enclosed metal parts are usually housed,packaged, boxed, enveloped, or placed in a container under suchconditions that water vapor and air are either present, or areintroduced to the metal parts at the time of their being disposedtherein, or Water vapor with air enters through the enclosure wallsafter' the packaging. I

It is an object of the present invention to obviate the above and otherdefects, and to provide novel products or materials, which may be usedas the'enclosing or packaging means per se, or therein, and whichmaterials are capable of inhibiting corrosion of metal parts stored ordisposed in such enclosing or packaging means and/or in said enclosuremeans containing said novel materials.

It has now been discovered that a product or Application October 28,1946, Serial No. 706,098

composition comprising a substantially solid (particularly fibrous)material having disposed thereon or therein one or more vapor phasecorrosion-inhibitors, the vapors of which have access to the contiguous,vapor space, prevents corroslon of corrodible metals disposed in theproximity of said compositions even in the presence of water vapor andoxygen. Suitable vapor phase inhibitors which are applicable accordingto this invention include salts of an organic nitrogen base with nitrousacid (organic base nitrites). Corrosion prevention was found to beeffectively provided particularly by compositions comprisingsubstantially solid covering materials containing organic nitrogen-basenitrites. It was also found that the vapor phase inhibitor shouldpreferably have at least a vapor pressure of about 0.00002 mm. Hg at 21C. Better results are obtainable with a vapor phase inhibitor having avapor pressure greater than about 0.0001 mm. Hg at 21 C. while a morecomplete inhibition of corrosion is obtainable with avapor phaseinhibitor having a vapor pressure greater. than about 0.001 mm. Hg at 21C. The above mentioned compositions provide a highly satisfactory meansfor maintaining a corrosion-inhibiting atmosphere in the proximity ofthe metal.

The compositions of the present invention may be realized and/orutilized in a number of ways which may differ in detail but not in theessentialities of the invention. Thus, these compositions may beprepared: by impregnating various cellulosic formulations with theinhibitors, by impregnating any sheet, film, fabric, or other partiallyporous or absorbent material with the inhibitors. Preferably the solidmaterial chosen for impregnation has at least a fibrous structure so asto allow for absorption of the vapor phase inhibitors between theindividual fibers of the carrier material. Where a carrier material isnot particularly absorbent, it may advantageously be coated with thepresent inhibitors.

It was found particularly effective to impregnate the vapor phaseinhibitors into a kraft paper which is either substantially neutral orwhich may be rendered neutral or somewhat basic in reaction byincorporation or impregnation therein of basic-acting materials,preferably an organic amine or other organic nitrogenou base.

, Representative examples of solid materials which are suitable forusein conjunction with the vapor phase inhibitors include: paper; textilefabrics, e. g. of cotton, wool, or silk; wood; modified or stiffenedpapers such as card-board, fibre-board, and laminated papers; syntheticfabrics or spun textiles such as rayons, polyamides, nylons,polyvinylbutyral, and polyethylene; asbestos, charcoal, activatedcharcoal, alumina gel, silica gel, etc. Any sheet or strip material madeof the above fibrous substances may be used to prepare the novelcompositions e. g. by coating. these substances with a solution,emulsion, or dispersion of the organic vapor phase inhibitofls) as IQlas the inhibitor may at least partially vaporize immune coating and thusbe present in the contiguous atmosphere;

Impregnation or deposition of the vapor phase inhibitors describedherein on any of the above solid materials is carried out by wetting,im-

mersion, or soaking of the material with a dispersion or solution of theinhibitoflsi prefer ably in a relatively volatile or'ganic solvent, in amutual solution of water-e'oluble organic mate rial and Water, or inwater alone. The impieg nation may also be effected by distributing amelt of the inhibitor(s) with or without a melt ing-point loweringagent, upon the surface of the solid carrier material. The fibrousmaterials may also be impregnated by contact with the vapors f e inors,- I ?1.?? meth Q i pregnation, however, com rises deposition of thei ii ofl i fr m j rtlq i e SOB est. 9 l- Vnts used being evapor'ated byconventional methods, as by use of elevated temperatures, preferably notinegcess of abjout 120? F. with or without air-blowing or the l3 l;e.Suitable solvents include methyl alcohol, ethyl alcohol, propyl alcohol,isopropyl alcohol, acetone, methyl ethyl ketone, di-isopropyl ether,ihethyl acetate, andlike volatile p olar organic materials.

, I In many cases it is advantageous to treat or impregnate one or norepaper laminates with the vapor phase inhibitorts) and then fabricatethese into finishedlaif'ninated fcomposition which contains outer layers(laminates) which are much less porous ondi stinctlyless impervious itthe repo t .o t ein bi lo fif l ma ge t impregnatedlaminates which maybe used for the interiorof a pa'ckage, or which are placed clo e to acorrodible metal, rn suchjeses, the outer laminate maybea metal foihsuchas tin or aluminum ,foil pi 'e'ferably ofsufficient thickiiessthat tcontains rid m en Similar re sults have alsobeen obtainedby coatingfo'ne side era vapor phase inhibitor-impregnated paper w ha fil b .waa,w h'su ;h W x a r co taining the inhibitor(s)', it is possible toenclose a metal objec t with onelayer of the paper, and effectivelypreventcorrosion. In another embodimentof the invention, kraft paperwaxed upon both sides wasw'armed to softenthe surface layer on one sidethereof, and crystals or powder of an organic nitrogen base nitrite wasthen sprinkled upon the softened wax. The latter was thencooled, andexcessvapor phase ine hibitor was shaken off. The resulting coated waxedpaper, was found to bean effective supplier of corrosion-inhibitingvapors. Other wellknown coating ,materials may be used in place of waxvfor dispersion or incorporation of the present. inhibitor(s) eitherbefore or after, disposal of the coating material upon suitable solidmaterials. As suchjco'ating materials, reference may. be made to:polyethylene blends of polyethylene with waxes, pol'yalkylene resins,alkyd resins j(e. g. of phthalicanhydride and glycerol), ethylcellulose, polyamide resins, etc.

Vapor phase inhibitors which have been found applicable for use in thepresentcompositions include salts of an organic nitrogen base withnitrous acid. Representative classes of nitrogenous bases which aresuitable for preparing the present inhibitor-salts include such bases,for example, as: primaryamines, secondary amines, tertiary amines,cyclic secondary amines of the type of piperidine, oxazines, morpholine,thiazolines and pyrrolidine; and various nitrogenous bases such as urea,thiourea, hydrazines, hy-

droxylamines, amidines, and guanidine. In any ious substituent groups oratomic radicals may be present so long as the sum total basicity of thenitrogenous compound is approximately equal to or greater than theacidity of nitrous acid with which itforms a salt. Among the substituentgroups, the alkyl ah'dcycloalkyl groups are preferred. Secondary aminenitrites, formed from nitrous acid and an amino nitrogen atom attachedto a'sec'ondary earbon of an organic radical, as typified by 'diisobutyl amine nitrite, di-isopropylamine nitrite, dicyclohexylaminenitrite, piperazine nitrite, morpholine nitrite, or 2, i,e,6-tetraniethyl tetrahydro-3-oxazine nitrite are particularly effectivevapor phase inhibitors.

'The basicity of'the yariousbasic nitrogenous constituents of the classof salts disclosed herein is de scribed, forle xaiiiple, the The OrganicChemistry of Nitrogen by V.'Sidgwick, 1937 edition. The many variousorganic nitrogenous bases are also described in fOrganic Chemistrybyiaul Karrer, i938 edition v V More specifically and preferably,organic nitrogen base saltsof nitrous acid include the following nitritesalts of 1. Primary amines such as t (a) primary amines in which theamine group is attached to a secondary or a tertiary aliphatic carbonatom as in the following structural forles:

whereinR'i, R2 and Rs are hydrocarbon radicals which are aliphatic,alicyclic, heterocyclic, aromatic, or alkylated cyclic radicals, andmay, if desired, fc ontai'n preferably not more than one olefinic doublebond, or R1 and R2 are joined in the form of'a cyclo aliphatic orhetero-cyclicalip-hatic ring radical R3.

(D) primary amines in which the amine group is attached to an aralkylgroup as in the following structural formula;

wherein R4 is an aromatic hydrocarbon radical, preferably a phenyl orallgyla'ted phenyl radical andnis an integer which is preferably 1 or 2;

(c) primary aliphatic amines, such as methyl amine, which react withnitrousacid in the p'res ence 'ofan excess of the amine to give aprimary amine nitrite salt (as distinguished from a primary aliphaticamine which reacts with nitrous acid to yield nitrogen, an alcohol, orother reaction product's).

2. Secondary amines, such as secondary amines ,inwhich the amine groupis attached to an aliphatic carbon atom, preferably a secondary ortertiary carbonatom, as represented by the following structuralformulas:

wherein R; and Re are hydrocarbon radicals as in l (ci'and wherein R;and R2 may be joined in the form of a ring forming A R: NH

which is either N-alicyclicor contains in the R3 portion of the organicring, atoms of the type of oxygen and/or sulfur.

3. Tertiary amines.

4. Quaternary ammonium bases pyridinium bases.

Specific examples of organic nitrogen bases suitable for preparation ofthe organic nitrogenbase nitrite salt vapor phase corrosion inhibitorsof the present invention include:

Primary amines: methylamine, isopropyl amine, Z-amino-butane, tertiarybutyl amine, 2- amino-l-methyl-pentane, various amyl, hexyl, heptyl,octyl, and higher homologous primary amines wherein the amine group isattached to a secondary or tertiary carbon atom; .cyclopentyl amine,alkylated cyclopentyl amines, .cyclohexylamine, mono-methylcyclohexylamines, dimethyl cyclohexylamines, trimethyl cyclohexylamines,otheralkylated cyclohexylamines, bornyl amine, fenchyl amine,cycloterpenyl amines, pinyl amine, benzylamine, betaphenylethylamine,alkylated benzylarnines, tetrahydrobetanaphthylamine, allyl amine,betamethyl allyl amine, beta.- chloro allyl amine, and their homologsand analogs.

Secondary amines: di-methyl-, di-ethyl-, di-npropyl-, di-isopropyl-,di-butyl-amincs; various secondary amines derived from amyl, hexyl,heptyl, octyl, and higher homologous alkyl groups; methyl isobutylamine, N-methy1 N- tertiary butyl amine, N alkyl N cyclohexyl amine,N-alkyl N-bornyl amine, di-bornyl amine, N-methyl N-cycloterpenyl amine,N-isopropyl N- l) -menthyl amine, N-alkyl N-benzyl amines and theirhomologs and analogs; dicyclopentyl amine, dicyclohexyl amine, alkylateddicyclohexyl amines; diphenylamine, dibenzylamine, di- (beta phenylethyl) amine; piperidine, piper azine, alkylated piperidines orpiperazines; 1,4- alkylated and unalkylated oxazines such as morpholi-neand 2,4,4,6-tetramethy1 tetrahydrol-1,3- oxazine; alkylated-L3-thiazinesuch as 2,4,4.,6- tetramethyl tetrahydro-3-thiazine.

Secondary amine type derivatives of alkylene diamines, such as:R1NH--R.:iNH-R3 wherein R1 and R3 may be like or different aliphatic,alicyclic, aralkyl, alkarylalkyl, heterocyclic, terpenic radicals, andwherein R2 is an alkylene or cycloalkylene radical. These R1 and R3radicals for instance, may be isopropyl, butyl, cyclohexyl, benzyl,and/or bornyl radicals. The R2 radical is preferably an ethylene orpropylene radical.

Tertiary amines: trimethyl amine, triethylamine, tri-n-propyl-amine,tri-isopropylamine, tributylamine, higher homologous and isomerictrialkylamines, variously N-substituted tertiary including amines havingdifferent organic radicals on the amino nitrogen atom, e. g., alkyl,alicyclic, bornyl,

'ienchyl, aralkyl, and like homologs and analogs;

and tertiary amine type derivatives of alkylene diamines.

Various organic nitrogenous bases particularly guanidine, alkylatedguanidines, alkylated thioureas, and also diazoles, imidazoles, imidazolines, e. g., 2-heptyl-2-imidazoline, die-zines, pyrimidines, and thebasic derivatives of these and other organic nitrogenous-base nuclei.

Quaternary ammonium bases; tetramethyl and higher tetra-alkyl ammoniumbases; trimethyl benzyl, trimethyl cycloheXy1-, tributyl' decyl ammoniumbases; various quaternary N-substituted ammonium bases having variousorganic radicals (of the type described above) on the quaternarynitrogen atom; pyridinium and alkylated pyridinium or qulnoliniumquaternary ammonium bases having an alkyl, cycloalkyl, or aralkyl groupon the quaternary nitrogen atom,

including methyl, butyl, cyclohexyl, benzyl groups basic in character.

The amount or concentration of the vapor phase inhibitor(s) which may bepresent in the compositions of this invention may vary within widelimits, but it is preferred to use them in the smallest efiectiveconcentrations. These are usually between about 0.05 gm. and about 5.0gm. of the inhibitor per square foot of the surface of the substantiallysolid material employed therewith. Especially satisfactory results areattained when the inhibitor concentration is such as to allow betweenabout 1.0 gm. and about 15 gm. (or for average conditions about 6 gm.)of the inhibitor for each cubic foot of enclosed vapor space.

Stability of the present vapor phase inhibitors, particularly thestability of organic nitrogen base nitrite salts, is usually adverselyaffected when they are present in a composition or an environment which,on contact with or dispersion in water, yields an aqueous phase having apH value of less than about 6. Also this stability is frequentlyadversely affected by elevated tempera tures, e. g., of the order of F.or F. These undesirable effects may be materially lessened or evenentirely obviated by the simul taneous presence of a basic-acting agent,i. e. of an alkaline agent or a compound which reacts as a base in thepresence of acidic-reacting materials. Preferably, it is advisable touse organic or inorganic compounds which, when dispersed in water, yieldan aqueous phase having a pH value of at least 7. As such stabilizers,reference may be made to amines, guanidine, alkaline and alkaline earthmetal hydroxides, carbonates and bicarbonatesand the like basicmaterials. The amount of such stabilizer should be between about 0.1%and about 25% by weight of the vapor phase inhibitor, although larger orsmaller amounts may also be used.

In cases where the absorbent, substantially solid material has a demandor chemical affinity for an organic base, particularly for the amineemployed to prepare the nitrite salt thereof as the inhibitor, it ispreferable to treat such solid absorbent material with the amine untilthis demand is satisfied.

The present compositions are improved, at least for certaincorrosion-inhibiting purposes, by having them contain a mixture of vaporphase corrosion-inhibitors, at least one of which has vapor pressurewhich is sufficiently high to pro vide immediate protection againstcorrosion while at least another inhibitor has a relatively low vaporpressure, which provides long-term corrosion-inhibition. The inhibitorwith the low volatility is retained substantially in the vicinity gem-17s 7 of the inetalte be protected and does not escape to any materialdegree through the covering materials. In manycases; as with waxed paperor a metal foil enclosure, the high vapor pressure corrosion-inhibitoris also retainedeffectively in the vicinity of the metal.

The novel compositions of the present invention may be employed in avariety of ways for preventing corrosion of metals normally corrodiblein the presence of air and water. The broad class of covering materialsdescribed herein containing the inhibitor(s) may be advantageouslywrapped over, cloaked around, inserted near, draped over, or otherwisedisposed in the immediate vicinity of the metal parts, so long as atleast suflicient exterior "covering is "provided tokeep an effectivecorrosion-inhibiting amount of the vapors arising from the presentcompositions in the proximity of 'the'metal to be protected. -Asillustrative examples, a layer of vapor phase inhibitor-containing paperwas inserted between every six or seven layers of steel ball bearings.About 16 sq. ft. of vapor phase inhibitor pa'per was used per paper boxcontaining approximately 2'50 steel bearings. The paper contained about1 gm. of di-cyclohexylammonium nitrite per sq. ft. of paper. Inspectionafter one month showed the bearings were completely protected from rust,whereas the hearings in a control test were badly rusted. Also, a paperdivider impregnated with di-isoproipyl or di-cyclohexyl ammoniumr'ii'trite and used inside each package of two large steel half-bearingswas found to keep the steel free from rusting. Also, a small piece ofvapor phase inhibitor-containing paper was enclosed within akraft-asphaltkraft laminate paper package containing bright bar steelstock. The latter remained unrusted, while like steel stock packaged inthe same type of a package, but without the present compositions, becamerusted. Many forms of steel military equipment including artillery guns,tanks, etc. have been draped loosely with vapor phaseinhibitor-containing paper, and kept within storage rooms. The equipmentwas found to have retained its initial rust-free condition -duringseveral months'of such storage. On the other hand, like equipment storedin the same manner, but without the presence of the presentcompositions, was found to have corroded.

For purposes of further illustration, reference will now be made to thefollowing examples, it being understood that there is no intention ofbeing limited to the specific conditions disclosed therein.

Example '1' Flat by 3 inch strips of thoroughly cleaned steel werewrapped in strong kraft paper which had been impregnated withdi-cyclohexylammo nium nitrite from a solution containing 20 weightpercent of the amine nitrite in a mixture of 75 weight percent methylalcohol'and weight percent water. The thus-wrapped pieces of steel wereplaced in an envelopemade of kraft-asphaltkraft laminated paper and thenexposed in a humidity cabinet to a temperature of 100 F. and 100%humidity fora period of seven days. At the end of this time the packageswere opened including those of control tests (in which 'kraft paperunimpregnated with a vapor ph'aseinhibitor was employed). The steelstrips wrapped with paper impregnated with the amine nitrite were foundto be free of corrosion and shiny.

The steel in the control test was very badly corroded with rust overpractically its entire surface. A like test was carried out in exactlythe same manner except 2 percent by weight of di-cyclohexylamine inaddition to the 20 weight percent .of the di-cyclohexylammonium nitritein the impregnating solution was used to impregnate the wrapping paper.In this test the steel was also protected perfectly from rusting.Independent experiments indicated that the life of thedicyclohexylammonium nitrite was increased materially by theimpregnation of the paper with di-cyclohexylamine.

. Example II 0.1 gm. pieces of 60 lb. kraftpaper were immersed-in a 2%by weight solution of *dicyclo hexylamine-in methanol-25% water solventmixture for 10 seconds and then dried 5 minutes with warm air. One dropof 0.01 N sulfuric acid solution added to an entire extract of suchtreated paper changed phenoiphthalein indicator over to the acid side. Asample of the described amine-impregnated paper was then tested in asealed glass tube stability test wherein 0.1 gm. of the paper onto whichwas deposited 0.05 gm. of dicyclohexylammonium nitrite, was subjected tothe vapors from 0.50 ml. of water. A tube for a control test wasprepared using a sample of the untreated paper. After the testingperiods indicated below, the contents of the tubes were analyzed fornitrite content, and the following results were obtained:

Percent of Nitrate Ions resent Duration at 212 F. lnfl'ours AmineTreated g g i Paper Example 'II I The presence of guanidine nitrite inpaper placed in the proximity of a strip of steel within an enclosure,completely prevents rusting and maintains the metal shiny. This test wascarried out under conditions of humidity at a temperature of 150 F. fora period of seven days. Similarly, .it was found that a strip of brasswas preserved free from corrosion when subjected to theco'nditionsdescribed herein. In the control tests the steel was badlyrusted and the entire surface of the brass was covered with a blue-graycorrosion film.

Example IV Kraft paper was passed twice through methyl alcoholcontaining 20 weight percent of di-cyclohexylammonium nitrite and 3weight percent of di-cyclohexylamine. The solvent was removed by thenpassing the paper over a metal drum dryer internally heated by infra-redlamps. Flat machined pieces of steel were wrapped in the thus-treatedpaper, and then placed in separate paper envelopes, the edges of whichwere sealed with wax. These envelopes were then suspended in a cabinetunder conditions of 100% humidity and a temperature of F. After 300hours of such exposure, only a few minute rust specks were present onthe steel protected by the im- .pregnated paper. On the other hand alike machined piece of steel in the control test was covered with rustspecks over its entire surface.

Example V The projecting outer surfaces of U-shaped machined steelstrips were wrapped with kraft paper containing about 1 gm. ofdi-cyclohexylammonium nitrite per sq. ft. of the paper, and thenoverwrapped with aluminum foil having 0.005 inch thickness, the lappededges of the foil being sealed with wax. A control sample of steel waswrapped in exactly the same manner except that plain unimpregnated kraftpaper was used. These samples were then suspended in a cabinet having100% of humidity, and maintained at 120? F. for 1000 hours. At the endof this period of time, there was no visible rust on any portion of thesteel pieces packaged in the containers hav-v ing the inhibitor. On theother hand, the steel of the control sample was badly rusted over morethan 75% of its surface.

percent solution of di cyclohexylammonium nitrite in methyl alcohol, andwas found to contain 1.6 grams of this organic nitrite salt inhibitor. Athird tube (as a control) contained no inhibitor.

A 5-inch section of each of said three tubes was placed in a 1 inch by 6inch Pyrex test tube. A inch by 5 inch steel strip was placed insideeach paper tube and the glass container test tube thereof was stopperedand maintained one hour at 120 F. Just before testing, the steel stripwas polished with No. 2/0 emery paper. The tests were continued for onehour at 120 F., and then the solid stopper was replaced by a corkstopper having a inch diameter hole, the test tube being then suspendedopen end down in a standard humidity cabinet held at 100 F. and 90%humidity. The results obtained are summarized in the following table:

. Appearance at Time in Hours Paper Tube Containing- Di-isopropylammonium nitrite no rust. no rust n ust no rust no rust no rust. Di-cyclohexyl ammonium nitrite. undo-.. mdo

do Do. None (control) rusting fine rust on faces, lightly more verylittle 11ttlechange httlechange.

on edges progressive rust. change.

edges. rusting;

B The lower one inch of tubes were moist.

Example VI rusted. For further comparison, like steel parts were firstcovered with a coating of a petroleum oil and then maintained at roomtemperature for eleven months. These steel parts showed a considerablenumber of rusted areas.

Example VII By impregnating two parts by weight, of asbestos fiber withone part of di-cyclohexylammonium nitrite and then using thiscomposition as dunnage for packaging steel articles, it is possible tokeep the steel surfaces of such articles free from rust.

Example VIII Four-ply spiral-wound kraft paper tubes, 18 inches long and0.75 inch outside diameter were used in the following tests. The layersof the paper tubes were held together with casein glue, the pH of thetube was 9.4 and titration to a pH of 7 of the water extract of thesepaper tubes before impregnation showed that on the averageeach one ofthem contained approximately 0.002 equivalent of basic-reactingmaterial.

One of these tubes was impregnated with a solution formed by dissolving40% by weight of di-isopropylammonium nitrite in a 50 weight percentaqueous solution of isopropyl alcohol. The tube was found to contain 3.5grams of diisopropylar'nmonium nitrite. Another one of these times wasimpregnated with a 20 weight specimens.

Example IX Two steel bolt specimens were prepared by solvent washing,followed by wire brushing and then screwed into the fitting nut just farenough that the latter actedas a. supporting base in which the boltstood in avertical position. Each of the prepared bolts was placedupright upon, the respective bottom of each of two 2-ounce samplebottles. In a prepared recess in the cork of the bottle containing thefirst of these specimens there was placed a small piece of cotton whichhad absorbed thereon 0.2 ml. of distilled water and 0.1 gm. ofmorpholine nitrite. The same amount of distilled water but without anyvapor phase inhibitor, was absorbed in the same manner on a piece ofcotton inserted into a prepared recess of the cork of the other of thetwo bottles. The respective bolts were not in contact with the cotton orthe materials absorbed in the cotton. These corked bottles were allowedto stand at normal room temperature for a period of 76 days. At the endof this test period, the steel specimen which was subjected to theaction of morpholine nitrite vapors was free from rust. The surface ofthis steel specimen was shiny as it had been at the start of the test.On the other hand, the other steel specimen was so severely rusted thatthe surface of it had a rusty appearance and had lost its original shinypolished surface.

Example X Two inch low-carbon steel plates were machined to a inch by 3inch strip and wire brushed to a bright metallic sheen. An inner wrap ofneutral kraft paper and an outer wrap of laminated metal foil paperprovided with an internal coating of a thermoplastic resin was providedaround one of the described steel-plate The outer laminated metal foilwrap was heat sealed. The other steel plate was packaged in theidentical manner except that the inner wrap of the neutral kraft paper,which in each instance measured 2 inches by 4 inches, was impregnated bydipping it in a 50% (by weight) 11 aqueous solution of morpholinenitrite. After dipping, the paper was dried by suspension'for about 10minutes in an air blast maintained at approximately 50 C. After suchdrying, the kraft paper contained approximately 0.1 gm. of theinhibitor.

Both specimens, after packaging, were inimersed in synthetic sea waterprepared according to U. S. Bureau of Ships Specification 14-0-45 (INT)(1934), for a period of 26 days, the water being maintained at atemperature of approxi mately 30 C. during the test. At the end of thetest period these packages were opened. Itwas discovered that the steelplate wrapped in paper which did not contain any amine nitrite was badlycorroded with rust. On .the other hand. they steel plate packaged withthe amine nitrite in theinner wrap retained its original. polished andunblemished condition and appearance.

Example XI Vapor phase corrosion tests were made with di--isopropylammonium nitrite to determine the effects on specimens of S. A.E. 1020 steel and 24 ST aluminum in coupled combination and also on theS. A. E. 1020 steel attached to asteel bolt. A one-half by one inchspecimen of the metal alloy, coupled by a steel bolt through holes ineach metal sample, was suspended in the vapor space of an 8 oz.wide-mouth bottle by means of a wire hook in a parafiined cork stopperof the bottle. A 16 sq. inch piece of kraft paper impregnated withapproximately 0.2 gm. of diisopropyhammonium nitrite, was placed on thebottom of a bottle of one series to be tested, while duplicate bottlescont'aining the metalsfor control experiments were prepared containingthe same amount of untreated. kraft paper. .To each of the containerswas added 012ml. of distilled water. All of thebottles were maintainedat 30 C. for '73 days, after which time the specimens were removed,uncoupled, inspected and the weight loss determined after removal of anycorrosion product, when present. It was found that, in the cases where,di-isopropylammonium nitrite was used, there wasno corrosion on eithermetal on the aluminum couple, and no corrosion (rust) on t e A. 02, t ld n the oi ltha d; in the control experiment (in which nodi-isopropylammonium nitritewas used) there was bad and uniform rustingof the steel and some corrosion of the aluminum on the S. A. E. 102 0steel-24 genome 12 line of Organic Nitrogen Compounds, UniversityLithoprinters, Ypsilanti, Michigan (1945), page 59, namely, to designatea radical obtained by the loss of a hydrogen atom from any hydrocarbon.

The present application is a continuation-in part of the copendingapplication Serial No. 557,358, filed October 5, 1944, now abandoned.

We claim as our invention:

1. A substantially solid material capable of inhibiting corrosion of ametal by an atmosphere containing oxygen and water vapor, whichcomprises paper containing between about 0.05 gram and about 5.0 gramsper square foot of the sur-' face of said paper, of di-isopropyl aminenitrite and a stabilizing amount of a basic-reacting agent.

2. A substantially solid material capable of inhibiting corrosion of ametal by an atmosphere containing oxygen and water vapor, which com-.

prises paper containing between about 0.05 gram and about 5.0 grams persquare foot of the surface of said paper, of di-cyclohexyl amine nitriteand a stabilizing amount of a basic-reacting agent.

3 A material capable of "inhibiting corrosion of a metal by anatmosphere containing oxygen and Water vapor, which comprises asubstantially solid fibrous material containing between about 0.05 gramand about 5.0 grams per square foot of the surface of said fibrousmaterial, of dicyclohexy amine nitrite and a stabilizing amount of abasic-reacting agent. A

4. A material capable of inhibiting corrosion of a metal by anatmosphere containing oxygen and water vapor, which comprises asubstantially solid fifrous material containing between about 0.05 gramand about 5.0 grams per square foot of the surface of said fibrousmaterial, of diisopropyl amine nitrite and a stabilizing amount of abasic-reactingagent. I

5. A material capable of inhibiting corrosion of a metal by anatmosphere containing oxygen and Water vapor, which comprises asubstantially solid fibrous material containing between about 0.05 gramand about 5.0 grams per square foot ST aluminum couple, and fine rushspecks over the entire surface of the steel.

Example XII A by 3 inch specimen of. aluminum was wrapped in 2 by 4 inchpieces of kraft paper im' pregnated with di-isopropylammonium nitritewhich was then placed in another envelope made by folding 5 by 5 inchpieces of Grade A paper; the last envelope was then sealed with apressure-sensitive,. waterproof tape. Another aluminum specimen wassimilarly prepared, the only difference being thatitwas wrapped in anuntreated piece of the said kraft paper. The envelopes or packages thusproduced were suspended over water at 30 C. for 2 months, whereupon itwas found that, whereas the aluminum specimen wrapped in the papertreated with diisopropylammonium nitrite was not corroded, the aluminumspecimen wrapped in the untreated paper had considerable whitecorrosion.

The term hydrocarbyl is used herein in accordance with the definition inDegering, Outof the surface of said'fibrous material, of dicyclohexylamine nitrite.

6. A material capable of inhibiting corrosion of a metal by anatmosphere containing oxygen and water vapor, whichcomp'rises asubstantially solid fibrous material containing between about 0.05grainandabout 5.0 grams per square foot of the surface of said fibrousmaterial, of a dicycloalkyl amine nitrite salt having a vapor piessureof at least about 0.00002 mm. Hg at 2 C.

7. A material capable of inhibiting corrosion of a metal by anatmosphere containing oxygen and water vapor, which comprises asubstantially solidfibrous material containing between about 0.05 gramand about Sgrams'per square foot of the surface of said. fibrousmaterial, of diisopropyl amine nitrite.

8. A material'capable of inhibiting corrosion of a metal by anatmosphere containing oxygen and water vapor, which comprises asubstantially solid fibrous material containing between about 0.05 gramand about 5 grams persquare foot of the surface of saidjfibrousmaterial, of a secondary amine nitrite salt having a vapor pressure ofat least about 0.00002 mm. I-Ig at 21 C.

9. A material capable of inhibiting corrosion of a metal by anatmosphere containing oxygen and water vapor. which comprises asubstantially solid fibrous material containing a corrosioninhibitingamount; of an organic nitrogen-base nitrite salt of an unsubstitutedhydrocarbyl amine, said salt having a vapor pressure of at least about0.00002 mm. Hg at 21 C.

10. A material capable of inhibiting corrosion of a metal by anatmosphere containing oxygen and water vapor, which comprises asubstantially solid fibrous material containing a corrosioninhibitingamount of an organic nitrogen-base nitrite salt having a vapor pressureof at least about 0.00002 mm. He at 21 C.

AARON WACHTER. NATHAN STILLMAN.

References Cited in the file of, this patent 14 UNITED STATES PATENTSNumber Name Date 1,387,132 Decherd Aug. 9, 1921 1,847,711 Calcott et alMar. 1, 1932 2,148,862 Kern Feb. 28, 1939 2,304,950 Parker et a1 Dec.15, 1942 2,323,369 Briggman July 6, 1943 2,344,404 Giloy Mar. 14, 19442,416,734 Boggs et a1 Mar. 4, 1947 OTHER REFERENCES Ex parte AppealNumber 5286, April 4, 1947, (Case Number 213) 29 J. P. O. S. 456.

Corrosion Handbook by Herbert H. Uhlig. Published by John Wiley andSons, Inc., New York, New York. in 1948. V V

10. A MATERIAL CAPABLE OF INHIBITING CORROSION OF A METAL BY ANATOMSPHERE CONTAINING OXYGEN AND WATER VAPOR, WHICH COMPRISES ASUBSTANTIALLY SOLID FIBROUS MATERIAL CONTAINING A CORROSIONINHIBITINGAMOUNT OF AN ORGANIC NITROGEN-BASE NITRITE SALT HAVING A VAPOR PRESSUREOF AT LEAST ABOUT 0.00002 MM. HG AT 12* C.